This invention relates to permanently stabilized polymers or copolymers containing hindered amine light stabilizers chemically bound to anhydride containing polymer or copolymer via diacyl hydrazide and/or N-(acylamino) functionalities.
Synthetic polymers such as polyolefins (e.g., polyethylene and polypropylene) styrenics (e.g., polystyrene, rubber modified polystyrene, ABS, etc.) polyvinyl chloride, polycarbonates, polyesters, and polyphenylene ethers are subject to degradation and discoloration upon exposure to heat and/or light with consequent deterioration of mechanical and other properties. Various stabilizers have been proposed to inhibit such deterioration. In addition to activity as a stabilizer, commercially useful stabilizer additives must have both excellent compatibility with and/or solubility in the polymeric substrate to be stabilized along with superior resistance to loss from the stabilized composition during processing and end-use application. Many stabilizer additives exhibit limited compatibility in certain substrates and excessive tendency to exude, sublime, and/or volatilize during weathering or processing of the stabilized compositions.
One approach to solving the volatility and migration problems of the stabilizers has been to prepare polymeric stabilizers. A preferred method in the industry is to attach stabilizer groups to existing polymers or copolymers containing reactive functionalities. Examples of said approach are as follows:
(i) Styrene-maleic anhydride copolymers and octadecene-maleic anhydride copolymers have been reacted with 2,2,6,6-tetramethylpiperidin-4-ol to provide semiesters containing a pendant HALS group (Canadian Pat. No. 1,180,496).
(ii) Cationic maleic anhydride homo- and copolymers were treated with 4-amino-2,2,6,6-tetramethylpiperidine to form the corresponding imide containing polymers. For example, an alternating maleic anhydride-styrene copolymer was treated with the above amine in xylene for 6 hours at 230.degree. C. to form the corresponding styrene-N-HALS-substituted maleimide which was used as a stabilizer for polypropylene. Similar N-substituted maleimide copolymers were prepared from 4-amino-2,2,6,6-tetramethylpiperidine and copolymers of maleic anhydride with 11-15 carbons olefins, propylene and isobutylene (Ger Offen 3,024,525).
(iii) Maleic anhydride modified polyolefins were further modified by reacting them with 4-amino-2,2,6,6-tetramethylpiperidine to form the corresponding N-substituted maleimide modified polyolefins (U.S. Pat. No. 4,520,171). Due to their higher molecular weights and the polyolefin backbone, they are more compatible with polyolefins than with conventional hindered amine light stabilizers.
(iv) Maleic anhydride copolymers were modified with 1-substituted-2,2,6,6-tetraalkyl-4-aminopiperidines (U.K. patent application B 2,145,100).